On a polynomial inequality

AbstractLet p(z)=a0+⋯+anzn and q(z)=b0+⋯ be polynomials of degree respectively n and less than n such that|p(z)|<|q(z)|,|z|<1. A result due to Q.I. Rahman states that|a0|+|an|⩽|b0|. In this paper, we slightly improve the above inequality and discuss several sharpness aspects, including all cases of equality

Lattice Boltzmann method for colloidal dispersions with phase change.

Colloidal dispersions are known to undergo phase transition in a number of processes. This often gives rise to formation of structures in a flowing medium. In this paper, we present a model for flow of a colloidal dispersion with phase change. Two distribution functions are used. The colloid is described as a non-ideal fluid capable of phase change, but rather than taking the dispersion medium as the second fluid, a better choice is the dispersion (water plus colloid) which can be considered as an incompressible fluid. This choice allows a standard Lattice Boltzmann (LB) model for incompressible fluids to be used in combination with for the 'free-energy' LB model for the colloid. The coupling between the two fluids is the drag force on the colloid and the dependence of the viscosity of the overall fluid on the particle volume fraction. The problems raised by characteristic times and lengths have been treated. The main application considered is the growth dynamics or domain structuration of protein dispersions during dead-end filtration on a membrane surface

Influence of barley malting operating parameters on T-2 and HT-2 toxinogenesis of Fusarium langsethiae, a worrying contaminant of malting barley in Europe.

The fungus Fusarium langsethiae, exclusively described in Europe at present, seems to have taken the place of other Fusarium species in barley fields over the last 5 years. It has proved to be a highly toxic type-A trichothecene producer (T-2 and HT-2 toxins). The aim of this work was to study the ecotoxinogenesis of this fungus the better to identify and manage the health risk it may pose during the beer manufacturing process. The influence of temperature and water activity on its growth rate and production of toxins are particularly assessed from a macroscopic point of view. Different cultures were grown on sterilized rehydrated barley with a water activity between 0.630 and 0.997 and a temperature ranging from 5 to 35°C. Biomass specific to F. langsethiae and T-2 and HT-2 toxins were quantified by real-time polymerase chain reaction and liquid chromatography-mass spectrometry, respectively. It appears that the optimal temperature and water activity for F. langsethiae toxinogenesis are 28°C and 0.997. This fungus was able to produce 2.22 g kg−1 of these toxins in 16 days on barley in optimal production conditions. The malting process seems to be a critical step because, in its temperature range, specific production was six times higher than under optimal temperatures for fungus growth. In the short-term, this work will help redefine the process conditions for malting. In the medium-term, the results will contribute to the development of a molecular tool to diagnose the presence of this contaminant and the detection of the toxins in barley, from fields to the end product

Mapping ecosystem services provided by wetlands at multiple spatiotemporal scales : a case study in Quebec, Canada

Abstract : Wetlands are affected by climate and anthropogenic changes, which influence the ecosystem services (ES) they provide. This study presents a spatially explicit quantification of wetland ESs. The study site is the Yamaska river watershed located in Quebec, Canada. The proposed approach includes four main steps: (1) statistical selection of function indicators (FI) to build a composite ecosystem service indicator (ESI); (2) temporal land use mapping for past (1984), recent (2011) and future scenarios (2050); (3) mapping and quantification of FIs and ESIs at all temporal and spatial scales; and (4) synthesis of multispatial and multitemporal information using a diagram representation. Results present the spatiotemporal evolution of the maintaining habitat ES provided by wetlands in the studied watershed. The historical characterization shows a general degradation of this service on the entire territory for the last 30 years. Multi-scale analyses can target priority sectors in which this service has deteriorated or is lacking. Future scenarios show the urgency to act in order to preserve currently intact areas because even the optimistic scenario indicates that the studied ES would not return to its 1984 state. Finally, the synthesis analysis provides a decision support tool adapted to territory managers. Thus, this study shows that the proposed multi-scale method is reproducible, robust and that it provides simple procedures to assess ES over time and space

Tree stem reconstruction from terrestrial laser scanner point cloud using Hough transform and open active contours

International audienceWe introduce an innovative methodology for reconstructing tree stems from terrestrial LiDAR data. The method uses a multi-scale combination of an original Hough transform and active contours. Tests were conducted on both simulated data and real LiDAR data. Even though no formal evaluation was completed yet, the procedure seems promising

Spatial vegetation density index from terrestrial laser scanner

International audienceForest monitoring is a key issue in scientific, social and commercial domains. Manual measurements of forests attributes can be tedious and limited, hence, Terrestrial Laser Scanner (TLS) has been introduced in forest monitoring. Vegetation density index (VDI) is a way to quantify vegetation using voxels from TLS data. The VDI is estimated using ray tracing techniques in a 3D voxel grid. This process can be time consuming. We present a continuous approach to minimise the ray tracing usage in the VDI computation

Modélisation de tiges d'arbres à partir de contours actifs

National audienceForest structural parameters are essential information for several applications, including forest inventory, forest management and allometric modelling. Recently, Terrestrial Laser Scanner (TLS) have been introduced as a reliable alternative to manual measurements of these parameters. In this study we present an innovative methodology for the estimation of diameter at breast height and tree stem tapper from a TLS acquired point cloud. Our work is based on a multi-scale combination of an original Hough transform and open growing active contours. The methodology was tested on both simulated data and real data acquired in natural forest environments. Even though no statistical results are available yet, the estimation procedure appears to be promising.Les attributs structuraux des arbres sont des éléments forestiers cruciaux. Ils se trouvent au coeur de multiples applications telles que l'inventaire forestier, la gestion forestière et les modèles allométriques. Récemment, les Scanners Lasers Terrestres (SLT) ont été présentés comme une alternative fiable à la mesure manuelle des paramètres structuraux. Dans cet article nous présentons une estimation innovante du diamètre à hauteur de poitrine et du défilement des troncs à partir de données acquises par SLT. Notre méthodologie utilise un schéma multirésolution dans lequel intervient une combinaison de transformée de Hough et de contours actifs croissants ouverts. Bien que des résultats chiffrés ne soient pas encore disponibles, les tests effectués sur des données simulées et réelles (acquises en environnement forestier naturel) montrent des résultats encourageants